package com.supersystem.utils;

import java.io.File;  
import java.io.FileInputStream;  
import java.io.IOException;  
import java.nio.MappedByteBuffer;  
import java.nio.channels.FileChannel;  
import java.security.MessageDigest;  
import java.security.NoSuchAlgorithmException; 

public class Md5Utils {
	  
	/** 
	* 默认的密码字符串组合，apache校验下载的文件的正确性用的就是默认的这个组合 
	*/  
	protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9','a', 'b', 'c', 'd', 'e', 'f' };  
	protected static MessageDigest messagedigest = null;  
	static{  
	   try{  
	    messagedigest = MessageDigest.getInstance("MD5");  
	   }catch(NoSuchAlgorithmException nsaex){  
	    System.err.println(Md5Utils.class.getName()+"初始化失败，MessageDigest不支持MD5Util。");  
	    nsaex.printStackTrace();  
	   }  
	}  
	  
	/** 
	* 适用于上G大的文件 
	* @param file 
	* @return 
	* @throws IOException 
	*/  
	public static String getFileMD5String(File file) throws IOException {  
	   FileInputStream in = new FileInputStream(file);  
	   FileChannel ch = in.getChannel();  
	   MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());  
	   messagedigest.update(byteBuffer);  
	   return bufferToHex(messagedigest.digest());  
	}  
	  
	public static String getMD5String(String s) {  
	   return getMD5String(s.getBytes());  
	}  
	  
	public static String getMD5String(byte[] bytes) {  
	   messagedigest.update(bytes);  
	   return bufferToHex(messagedigest.digest());  
	}  
	  
	private static String bufferToHex(byte bytes[]) {  
	   return bufferToHex(bytes, 0, bytes.length);  
	}  
	  
	private static String bufferToHex(byte bytes[], int m, int n) {  
	   StringBuffer stringbuffer = new StringBuffer(2 * n);  
	   int k = m + n;  
	   for (int l = m; l < k; l++) {  
	    appendHexPair(bytes[l], stringbuffer);  
	   }  
	   return stringbuffer.toString();  
	}  
	  
	  
	private static void appendHexPair(byte bt, StringBuffer stringbuffer) {  
	   char c0 = hexDigits[(bt & 0xf0) >> 4];  
	   char c1 = hexDigits[bt & 0xf];  
	   stringbuffer.append(c0);  
	   stringbuffer.append(c1);  
	}  
	
	/**
	 * 检查密码
	 * @param password
	 * @param md5PwdStr
	 * @return
	 */
	public static boolean checkPassword(String password, String md5PwdStr) {  
	   String s = getMD5String(password);  
	   return s.equals(md5PwdStr);  
	}  
	
	public static void main(String[] args) {
		System.out.println(Md5Utils.getMD5String("admin"));
	}
}  

